Power unit for brake systems



March 28, 1950 R. R. GUNDERSON 2,502,378

POWER UNIT FOR BRAKE SYSTEMS Original Filed Jan. 6, 1945 2 Sheets-Sheet 1 March 28, 1950 R. R; GUNDERSON POWER UNIT FOR BRAKE SYSTEMS Original Filed Jan. 6, 1945 2 Sheets-Sheet 2 Patented Mar. 28, 1950 UNITED STATES TENT OFFICE POWER UNIT FOR BRAKE SYSTEMS Ralph E. Gunderson, Chicago, Ill.

4 Claims.

provide suction motor booster, for the trailer brakes.

vAnother object of the invention is to provide an improved power unit, including suction booster for the trailer brakes, wherein the valve to the booster will be controlled normally by the pressure from the pedal actuated master cylinder of the tractor, but in an emergency the same valve may be controlled by a hand valve on the tractor or automatically by a relay valve on the trailer.

Another object of the invention is to provide an improved operating cylinder for the trailer brakes wherein the pressure on the fluid coming from the master cylinder is increased.

Still another object of the invention is to provide a liquid reservoir for the operating cylinder on the trailer, which will enable air to escape from the cylinder when the brakes are released and cause liquid to fill the space left by the air. Of course, said reservoir will be automatically closed when pressure is applied to the operating cylinder.

The present application is a division of my application Serial No. 52 1583, filed January 6, 1945, now Patent No. 2,463,l72,for a Power brake system.

The invention is illustrated in a preferred embodiment, in the accompanying drawings, in which- Figure l is a longitudinal sectional View of the operating cylinder, suction booster motor and relay valve for a trailer; Fig. 2, a diagrammatic View of a brake system for a tractor and trailer; Fig. 3, a fragmentary sectional view of the operating cylinder shown in Fig. 2, but in the position where pressure is applied to the brake cylinders; and Fig. 4, a vertical sectional View taken as indicated at line of Fig. 1.

One form of the improved brake system is illustrated diagrammatically in Fig. 2, wherein a broken section line 5 separates the tractor side at the left from the trailer side at the right. A master cylinder t, actuated by a brake pedal 1,

is adapted to force brake liquid through a conduit 23 to the truck operating cylinder 9, and by means of a communicating conduit is to a trailer operating cylinder l l. The trailer has a socket connection 52 for a coupling hose it, which is shown in my Patent No. 2,393,679, issued January 29, 1946.

A suction booster motor i l on the tractor assists the operating cylinder 9 in forcing liquid through the conduit l5 to the wheel brake cylinders of the tractor. An intake manifold 55 on the tractor may be the source of suction for both the tractor and trailer. A conduit ll, provided with a check valve it", leads to a tractor suction reserve tank it, which connected to the booster motor by suction line The suction motor i4 is shown and described in my Patent No. 2,406,328, issued August 27, 1946. A suction line 26 is connected to the suction line i 3', through is shown in detail in Figure 'l.

a manually operable valve 22, which may shut ofi the line 2i from the suction line or admit air into said line H. The line it connects up with the trailer through a detachable hose connection provided with a shut oil cook 25.

The operating cylinder ii on the trailer is provided. with a suction booster motor 25, which A conduit 26 from the operating cylinder leads to the brake cylinders on the wheels of the trailer. A suction reserve tank 2'! is provided on the trailer, and is connected to the main suction line 2 through a check valve 28. A suction, conduit 2'3 leads from the suction tank to the booster motor, and is normally controlled by valve 38, but is pr vided with an emergency relay member L l, which is connected at one side by a conduit 32 to the suction tank. and is connected on the other side to a conduit to the main suction line 2i.

Referring now to the power unit on the trailer, shown in Fig. 1, a main operating cylinder 34 is mounted on the trailer and is provided on its low pressure side with an auxiliary cylinder 35, or slightly lar er diameter, which communicates with the master cylinder the tractor by means of the conduit 6 A liquid reservoir tank 35 is provided on the top side of the cylinder E i, and has the usual filler cap iii. A port 3-8 connects the reservoir to the rear portion of the cylinder 3t.

A hollow piston 35) is provided in the cylinder 34, and forms a small cylinder is for a piston ti, which actuates a push rod t2 by a yielding compression spring A hollow multiple head piston it has one head in the auxiliary cylinder 35, and a smaller diameter head in the cylinder 3 34. The smaller piston head d5 is adapted to bear against the end of the piston 39 when the brakes are released, as shown in Figure 1. When pressure is applied from the master cylinder to the conduit iii, the booster motor is energized by movement of the small piston All and will pull the piston 35% beyond the reservoir ort 38 so as to cut it off from the conduit 26. The piston t5 is forced to follow the piston 39' to the position illustrated in Fig. 3, and holds the port 38 closed.

The lower front portion of the auxiliary cyl-- inder 35 is vented to atmosphere, so that any pressure from the master cylinder will urge the piston assembly towards the piston The piston head M is larger in cross-sectional area than the piston head $5, so that pressure from the master cylinder will cause the piston 35 to follow the piston and close the port 33.

The suction booster motor and valve is similar to that shown in my said Patent No. 2,406,328, r

and has a metal casing 45 provided with a diaphragm ll, which is secured to the piston rod 39, and is urged forwardly by means of a conical spring G8. The booster motor valve is enclosed in a housing 49, and contains a seat 59 for a dome shaped valve member 55, which is adapted to close the suction line The valve member 5! is urged to closed position by means of a conical spring 52.

The push rod 32 makes a sliding fit through the diaphragm ll, and has a bifurcated end which is connected to a ring member 53, carried by a flexible diaphragm 5 5 which has one side communicating with atmosphere through a filter vent 55, and the other side communicating with the interior of the motor casing 46. The ring member 53 is also connected to a spider-like member "36, which extends through the end oi the housing 59, and is connected to the flexible diaphragm 51 of the relay member 3|. A coil spring 58 urges the ring member 53 to the position shown in Figure 1, so that atmospheric pressure may enter through the member 55 and through the ring 53 to the inside of the motor casing. It will be understood that when the push rod t2, as viewed in Fig. l, is moved to the right by pressure from the master cylinder through the conduit ill, it will cause the ring member 53 to engage the valve member 5! and shut ofi the communication with atmosphere. Further movement of the ring member 53 to the right will open communication, between the conduit 29 and the interior of the motor housing, causing the suction pressure to draw the piston 39 to the right and force brake liquid through the conduit 25 to the wheels. This is the way the brakes are normally operated from the tractor by pressure on the foot pedal i.

If movement of the pedal is stopped, atmospheric pressure on the diaphragm fi l will compress the spring 43 and shut oi? the suction line, and if the piston 39 is moving to the right under the influence of the booster, pressure will be reduced on the small piston 4i and will further facilitate the closing movement of the valve. As the operating cylinders of the tractor and of the trailer are each connected to the master cylinder, pedal pressureeifects the simultaneous operation of both. This operation of a power cylinder is described in my said Patent No. 2,406,328.

In the event that the main suction line 2| should be broken, or air admitted through the valve 22, pressure would be increased on the left of the diaphragm M, as viewed in Fig. 1, through the conduit 33, and as suction would be exerted on the opposite side of the diaphragm 5'3 by the conduit 32 to the suction tank, the ring 53 would be moved to the right and the suction motor operated to set the brakes.

Thus it will be understood that breakage of the main suction line 2| would set the brakes on the trailer automatically, or, should the conduit it to the master cylinder be broken, the operator may set the brakes on the trailer by means of the valve 22.

The foregoing detailed description is given for clearnes of understanding only, and no unnecessary limitations should be understood therefrom, for some modifications will be obvious to those skilled in the art.

I claim:

1. A power unit in a hydraulic brake system comprising: an operating cylinder communicating at its rear end with a pedal actuated master cylinder and at its opposite end with a wheel cylinder; a reservoir on said cylinder having a port into the rear portion of the cylinder; a piston in said operating cylinder adapted to open said port when in its rearmost position; an auxiliary cylinder of slightly larger diameter axially disposed on the master cylinder end of the operating cylinder and communicating therewith, said auxiliary cylinder having its front side vented to atmosphere; a hollow multiple piston having one head in the auxiliary cylinder and another head in said operating cylinder adapted to engage the rear end of the first mentioned piston during a portion of its travel to close the reservoir port; a suction booster motor having a movable member connected to said first mentioned piston; a

valve for connecting said booster motor with pressure or a suction line; and means for actuating said valve including a small cylinder communicating with the master cylinder, a piston in said small cylinder, 2. push rod connecting said last mentioned piston and valve, and a small flexible diaphragm connected to said push rod and having one side communicating with at mosphere and the opposite side with said suction motor.

2. Apparatus as specified in claim 1, in which the push rod makes a yielding connection with the piston in the small cylinder by means of a compression spring.

3. A power unit as specified in claim 1, in which the small cylinder serves as a hollow piston rod which connects the booster motor and the first mentioned piston.

4. Apparatus as specified in claim 1, in which a suction reserve tank is connected through a check valve to a main suction line, the booster motor valve is connected by a suction line to said tank, and a relay valve is provided for emergency operation of the booster motor valve, said relay valve having a diaphragm connected to said booster motor valve and having one side of said diaphragm communicating with the reserve tank and the other side with said main suction line.

RALPH R. GUN'DERSON.

REFERENCES CITED The following references are of record in the file or" this patent:

UNITED STATES PATENTS Number Name Date 2,352,357 Almond June 27, 1944 2,406,328 Gunderson Aug. 27, 1946 

